Felicity Rich on fri 9 mar 07
Hi John,
I just bought your book and was very excited about the Carribean Sea Green
glaze. We only have a gas kiln and fire reduction. Can it be fired in
reduction, and are your results primarily based on oxidation firingg?
Regards,
Felicity Rich
Quoting Leigh Whitaker :
> In a message dated 3/9/2007 3:29:33 P.M. Eastern Standard Time,
> hesselberth@MINDSPRING.COM writes:
>
> Hi Leigh,
>
> Caribbean Sea Green turns from blue to green as the rutile
> concentration increases. Look at the pictures in the book and you
> will see that at 4.5% it is blue and at 6% it is green. But rutiles
> are quite different and some potters have had to increase the rutile
> level to 8 or even 10% to get it to go green. An occasional potter
> has never been able to get the green with rutile they were using. I
> used "Dark Rutile" when I developed the recipe, but whether the dark
> rutile of today is similar enough to that of 5 years ago, I don't know.
>
> Anyhow what I would do is take a small amount of the glaze you have
> mixed, estimate the dry weight of what you use, and then add rutile
> in a couple increments so you get into the 8-10% range and see what
> happens. Also make sure you are really getting the glaze dispersed
> well. Since your slop is thin, some of the rutile may have settled
> out to the bottom of your bucket.
>
> Regards,
>
> John
>
>
> Hmm, okay. That makes sense. I was looking at the pictures of the various
> blues vs. the Caribbean Green, and marveling that the rutile percentage
> would
> make that much of a difference, very neat. For that reason I wasn't so
> surprised that mine turned out more bluish. A little while ago I just held
> the
> pot that I brushed up to the picture in the book, and it's really not that
> far
> off. The dipped one, however, is definitely blue. I can't remember
> exactly
> when I did the dipped one in relation to when I did the brushed ones (with
> regards to my dilutions and pouring off water and adding CMC). The rutile
> settling may very well be the difference.
>
> I will try the additions of increments of rutile as well.
>
> Thanks!
> Leigh
>
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John Hesselberth on sat 10 mar 07
Hi Felicity,
Many of our glazes do fine in reduction; however, Caribbean Sea Green
is one we can't recommend for reduction firing. It is a zinc-
containing glaze and zinc oxide is easily reduced to zinc metal.
Unfortunately zinc metal is very volatile, boiling at 907 Celsius
(1665 F). So in a reduction atmosphere, most if not all the zinc will
go up your stack. Others of our glazes that probably are not suited
for reduction firing would be Waxwing Brown and Waterfall Brown.
They have a high iron content and iron is reduced and turns into a
flux in reduction. They would probably end up as a puddle on the
floor of your kiln.
But the high calcium semimattes as well as the glossy bases and most
of their color variants should be fine in reduction. Over the last
couple years several people have told us they have been using them
that way with success. They can be a good starting point for people
who are moving from cone 10 reduction down to cone 6 reduction for
energy savings--and we hear of more and more people doing that
regularly these days.
Since they were designed to be fired at cone 6, that is probably a
better way to start than by trying to "adjust" cone 10 glazes down to
cone 6. Too many attempts to do that that I have seen have resulted
in glazes with too little silica and/or alumina to be good, durable
glazes for use on functional work.
Regards,
John
On Mar 9, 2007, at 7:54 PM, Felicity Rich wrote:
> Hi John,
>
> I just bought your book and was very excited about the Carribean
> Sea Green
> glaze. We only have a gas kiln and fire reduction. Can it be fired in
> reduction, and are your results primarily based on oxidation firingg?
>
> Regards,
>
> Felicity Rich
>
>
>
> Quoting Leigh Whitaker :
>
>> In a message dated 3/9/2007 3:29:33 P.M. Eastern Standard Time,
>> hesselberth@MINDSPRING.COM writes:
>>
>> Hi Leigh,
>>
>> Caribbean Sea Green turns from blue to green as the rutile
>> concentration increases. Look at the pictures in the book and you
>> will see that at 4.5% it is blue and at 6% it is green. But rutiles
>> are quite different and some potters have had to increase the rutile
>> level to 8 or even 10% to get it to go green. An occasional potter
>> has never been able to get the green with rutile they were using. I
>> used "Dark Rutile" when I developed the recipe, but whether the dark
>> rutile of today is similar enough to that of 5 years ago, I don't
>> know.
>>
>> Anyhow what I would do is take a small amount of the glaze you have
>> mixed, estimate the dry weight of what you use, and then add rutile
>> in a couple increments so you get into the 8-10% range and see what
>> happens. Also make sure you are really getting the glaze dispersed
>> well. Since your slop is thin, some of the rutile may have settled
>> out to the bottom of your bucket.
>>
>> Regards,
>>
>> John
>>
>>
>> Hmm, okay. That makes sense. I was looking at the pictures of
>> the various
>> blues vs. the Caribbean Green, and marveling that the rutile
>> percentage
>> would
>> make that much of a difference, very neat. For that reason I
>> wasn't so
>> surprised that mine turned out more bluish. A little while ago I
>> just held
>> the
>> pot that I brushed up to the picture in the book, and it's really
>> not that
>> far
>> off. The dipped one, however, is definitely blue. I can't remember
>> exactly
>> when I did the dipped one in relation to when I did the brushed
>> ones (with
>> regards to my dilutions and pouring off water and adding CMC).
>> The rutile
>> settling may very well be the difference.
>>
>> I will try the additions of increments of rutile as well.
>>
>> Thanks!
>> Leigh
>>
**************************************
AOL now
>> offers free
>> email to everyone. Find out more about what's free from AOL at
>> http://www.aol.com.
>>
>>
> ______________________________________________________________________
> ________
>> Send postings to clayart@lsv.ceramics.org
>>
>> You may look at the archives for the list or change your subscription
>> settings from http://www.ceramics.org/clayart/
>>
>> Moderator of the list is Mel Jacobson who may be reached at
>> melpots@pclink.com.
>>
>
> ______________________________________________________________________
> ________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
Chris Trabka on mon 12 mar 07
Felicity,
If you are interested in cone 6 reduction glazes, Diana Pancioli researched
the topic and came up with a series of cone 6 reduction glazes that provide
the surface, color, and texture that is generally available at cone 10. The
link
http://www.ceramicsmonthly.org/cmpc/richcontent/GlazeForward-0606.pdf is
from the article published in Ceramics Monthly.
Chris
>Hi John,
>
>I just bought your book and was very excited about the Carribean Sea Green
>glaze. We only have a gas kiln and fire reduction. Can it be fired in
>reduction, and are your results primarily based on oxidation firingg?
>
>Regards,
>
>Felicity Rich
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